This section is intended to provide the background for understanding the detailed description that follows. It is not intended to enlarge the scope of admitted prior art beyond what a skilled person would have beheld before reading the present description. While the background comprises prior art, it may also comprise the inventors' observations, discoveries, identification of heretofore unappreciated deficiencies or problems and insight into solving them. As such, this section may comprise description of inventive elements that is not prior art and that is not is admitted as such.
The pitot-static system is a system of pressure-sensitive instruments that is used in aviation to determine several variables related to aircraft behavior such as airspeed, altitude and altitude trend. Typically, a pitot-static system on an aircraft comprises a pitot tube, one or more static vents and pitot-static instruments. The pitot tube points directly into the airflow and receives air pressure caused by the flow. The static vent comprises a static port, which is an opening on the aircraft body at a location that is at ambient pressure such that the static port receives an air pressure generally equivalent to that of the ambient air around the aircraft. Based on the pressures provided at the pitot tube and at the static port, instruments compute certain flight-related variables such as airspeed.
Static ports are typically a flush hole on the fuselage of aircrafts. Disturbed airflow at the static port can lead to instrumental inaccuracies. As such, static ports are typically located in an area where airflow is relatively undisturbed and the static vent may include an area around the static port that is kept clean (often unpainted) to avoid disturbing airflow.
Static ports are typically located in regions where the local air pressure is equivalent to the ambient air pressure around the aircraft. Typically, this may be on a side of the fuselage. However, some factors such as side-slippage and crosswinds may affect the pressure perceived at the static port. To counter this, many aircraft comprise two static ports, one on either side of the aircraft body, allowing them to take an average pressure in order to achieve more accurate instrumental computations.
Proper functioning of the pitot-static system is critical to the safe operation of aircraft since data derived by the system, such as altitude, is safety-critical. As such, pitot-static systems are typically tested regularly to ensure proper functioning. Such tests are typically required for certification.
As part of the pitot-static system test, equipment is typically provided on the pitot tube and/or static vent to provide pressure in the form of positive pressure or negative pressure to simulate higher or lower pressures at the pitot tube and/or static port. FIG. 1A illustrates a static vent 105 found on the fuselage of an aircraft body 100. The static vent 105 comprises a static port 115 which is an opening of the pitot static system to the exterior. The static port is located at on a part of the aircraft body where the air pressure may be used to ascertain ambient air pressure. The static vent 105 also comprises a clean body portion 110, which is an area of the aircraft body 100 surrounding the static port 115 which is kept clean and free of airflow-disrupting elements.
Typical pitot static system tests require the equipment to be affixed to the aircraft body 100 in such a way as to create a sealed passage between the test equipment and the static port 115. To that end, threaded holes 120 or the like may be provided allowing the equipment to be fastened to the aircraft body 100. This requires such threaded holes 120 to be designed into the aircraft, despite having potentially no use outside of pitot static system testing. Other equipment may use suction to hold against the aircraft body 100 which may be expensive to manufacture or be unreliable. In both cases, installation is complicated and requires accessing the static vent 105 by hand.
Oftentimes, aircraft will have multiple static vents near one another as is shown in FIG. 1B, where two static vents are provided on the side of an aircraft fuselage. Typically the static vents will be provided in a zone 125 marked by a marker 130.